使用空間前饋架構於寬頻管路主動噪音控制系統之分析與數位信號處理實現

Abstract

從聲學與控制的觀點，可發展出使用空間前饋控制架構於寬頻管路消音之主動控制技巧。 根據Munjal與Eriksson於1988年之研究，對於此主動噪音控制(ANC)問題存在一理想控制器。 此理想控制器為一有限聲源阻抗之函數，且與管路上下游之條件無關。 儘管具此簡單性，由於穩定性問題與校正機電聲常數之困難，無法實際地實現此一理想控制器。 因此，透過Roure於1985年提出之等效控制器，可實現此理想控制器。 然後，使用FIR，IIR與混合法 (FIR加IIR) 三種不同的方法實現Roure之控制器於數位信號處理器上。 此ANC實驗顯示：在300-600 Hz 頻寬內，最大可達15 dB 之消音量。 另外，在本論文也將探討實際之實現方法與設計等考量。

The active control technique for broadband attenuation of noise in ducts, using spatially feedforward structure, is investigated from the viewpoint of both acoustics and control engineering. According to the previous work by Munjal and Eriksson (1988), there exists an ideal controller for this ANC problem. The ideal controller is a function of the finite source impedance, whereas it is independent of the upstream and downstream conditions. Despite of its simplicity, the ideal controller cannot be practically implemented due to stability problem and difficulties of calibration of electro-mechanical-acoustical parameters. Alternatively, the controller is implemented via an equivalent formulation that is a refinement from the original controller proposed by Roure (1985). The modified Roure’s controller is then implemented on a DSP platform, using three different approaches: FIR filter, IIR filter and hybrid filter (FIR and IIR). Experiments were conducted to validate the proposed ANC system. The results showed that the system achieved 15 dB maximal attenuation in the frequency band 300-600 Hz. The issues concerning practical implementations and design considerations are also discussed in the paper.